Electrodeposition of bright nickel



United States atent No Drawing. Filed Mar. 22, 1960, Ser. No. 16,654

10 Claims. (Cl. Mid-49) V 'l];h;'s invention relates to the electrodeposition of bright me e Nickel electrodeposits as plated are not bright in thicknesses substantially greater than those of very thin strike or flash coatings. It is possible to obtain bright deposits in substantial thickness with the use of bath additives. Addition agents useful as brighteners in nickel plating baths are generally divided into two classes on the basis of their predominant function. Secondary brighteners are materials which produce brightening and grain refining effects, resulting in semi-bright and lustrous deposits. The addition of primary bri'ghteners together with the secondary brightener results in deposits that are mirror-bright. Although many materials have been proposed as effective secondary brighteners, very few have had any successful commercial utilization. We have now discovered a new secondary brightener.

It is an object of this invention to provide an efficient process for electrodepositing bright and smooth nickel deposits.

Another object of this invention is to provide bath compositions for bright nickel plating.

The invention also contemplates providing novel brighteners for use in nickel plating baths.

We discovered that sulfonated dibenzothiophene dioxide is an effective secondary brightener useful in a variety of nickel plating baths. When used in conjunction with a primary brightener, mirror-bright deposits are obtained. The sulfonated dibenzothiophene dioxide compounds have the following general formula:

-SO X V Y a s wherein Y is hydrogen or SO X, and X is a cation whose presencein the bath is not deleterious and includes the alkali metals and the alkaline earth metals. X is preferably hydrogen, ammonium, sodium, potassium, nickel, cobalt, or magnesium. The sulfonated dibenzothiophene dioxide is used in amounts between '1 g./l. and g./-l., and preferably 2 g./l. and 6 g./l. in both bright and semibright baths.

Sulfonated dibenzothiophene dioxide may be synthesized by a number of routes. A preferred preparation is the sulfonation of diphenyl with fuming sulfuric acid oleum) for about two hours, isolating and neutralizing. The reaction product is generally a mixture of the mono-, di-, and tri-substituted compounds (with the trisubstituted compound beingpresent in major proportions) having the following general formula:

The mixed reaction product is an elfective brightener. The mono, di-, and tri-substituted compounds are each individually effective as" brighteners. Sulfonated dibenzoby a moving cathode.

thiophene dioxide may also be synthesized by the hydrogen peroxide oxidation of dibenzothiophene followed by sulfonation with fuming sulfuric acid.

Conventional baths and processes for electroplating bright nickel are dscribed in Principles of Electroplating and Electroforming, Blum and Hogaboom, pages 362- 381, revised third edition, 1949, McGraw-Hill Book Co., Inc, New York; and Modern Electroplating, edited by A. G. Gray, The Electrochemical Society, 1953, pages 299-355. The control and operating conditions, including the concentration of the bath ingredients, pI-I, temperature, cathode current density, etc., of these conventional baths are generally applicable to the present invention. Practically all baths for electroplating bright nickel contain nickel sulfate, a chloride, usually nickel chloride; a buffering agent, usually boric acid; and a wetting agent, e.g., sodium lauryl sulfate, sodium lauryl ether sulfate, and 7-ethyl-2-methyl-4-undecanol sulfate. Such types of baths include the well-known Watts-type bath and the high chloride type bath. Other bats contain as the source of the nickel a combination of nickel fluoborate with nickel sulfate and nickel chloride, or a combination of nickel fluoborate with nickel chloride. Typical Watts-type baths and high chloride baths are noted in Tables I and II.

pH 2.5 to 4.5 electrometric agitation.

Sulfonated dibenzothiophene dioxide is compatible with a Wide variety of primary brighteners. Preferred brighteners used in combination therewith include acetylenic alcohols and amides, Z-mercaptobenzimidazole and its amino substitution products, diethylene triarnine and other polyamines (such as tetraethylene pentamine), triphenylmethane dyes, and such pyridine and quinaldine derivatives as: a-pyridinium-l-methylquinaldinium dimethosulfate, a,a'-(2,6-lutidinylene) bis(pyridinium iodide), and 1-(2-quinolylmethyl) pyridinium iodide. Eifective bright plating baths have been developed utilizing the sulfonated dibenzothiophene dioxide'as the secondary brightener, together with a primary brightener, and an auxiliary secondary brightener such as 2-butene-l,4-diol or N-vinyl-Z- pyrrolidone, as illustrated in Examples 2 to 9, 13, 17 to 22, 27 and 28.

For the purpose of giving those skilled in the art a better understanding of the invention, illustrative examples are given. In each of the examples, an aqueous acidic nickel-containing bath 'was made up with the specified components. Electrodeposition was carried out by passing electric current through an electric circuit comprising an anode and a sheet metal or rod cathode, both immersed in the bath. The baths were agitated, usually The examples utilizing the sulfonated dibenzothiophene dioxide together with a primary brightener resulted in mirror-bright deposits. The deposite of Examples 16 and 26 wherein the secondary brightener was used alone resulted in fine-grained, uniformly semibright deposits having good duc ility.

In Examples 1 through 16, the following standard Watts-type bath was used as a base solution:

Example 12 Amount, g./l. Sulfonated di-benzothiophene dioxide Nickel sulfat-e 300 Polyoxyethylated 2-butyne-1,4-diol 17s 0.012 Nickel chlonde 60 g./l. Sodium law Is ulfate 025 Boric rid 45 g./1. Y pH 3.0 to 4.5. Example 13 Temperature 38 to 66 Sulfonated dibenzothiophene dioxide 4 2-butene-1,4-diol 0.26 v Example 1 Amount g Ethylnyl cyclohexanol 0.012 .Sulfonated dibenzothiophene dioxide 4 Sodmm lauryl sulfate 4,4,4"-triaminotriphenylmethane 0.005 Example 14 Sodmm lauryl sulfate Sulfonated dibenzothiophene dioxide 4 Example 2 'S-sulfanilylindazole 0.005 Suifonated dibenzothiophene dioxide 1 Sodium lauryl Sulfate Sodium 1,3,6 naphthalene trisulfonate 20 Example 15 fi 'K M1 Sulfonated dibenzothiophene dioxide 4 N'WDYI'Q'PYIOhdOHe Phenylpropiolamine 0.2 Sodlum lauryl sulfate Diethylene triamineua; 0.002 Example 3 Sodium lauryl sulfate 0.25 Sulfonated dibenzothiophene dioxide 4 Example 16 zmFrcaptobenzlPndazole Sulfonated dibenzothiophene dioxide 4 N'Ymyl'z'Pyrmhldone Sodium lauryl sulfate 0.5 Sodium lauryl sulfate 0.5

E le 4 In Examples 17 through 26, the following high chloxamp ride aqueous bath was used as a base solution: Sulionated dibenzothiophene dioxide 4 Nickel chloride 240 gJL z-mecapwbenzmdazole 1 Nickel Sulfate 60 y -py 1.0 Boric acid g. Sodium lauryl sulfate 0.25 PH 3.0 to 4.5

Example 5 Temperature 38 to 66 C. Sulfonated dibenzothiophene dioxide 4 Example 17 a-Phenyl propynol 0.01 Amount, g./l. Propargyl alcohol 0.005 S ulfonated dlbenzothiophene dioxide 4 2-butene-1,4-dio1 0.2 2m eroapt0benz1m1dazo1e 0.01 Sodium lauryl sulfate 0.5 N-v nyl-2-pyrrohdone 0.2 Example 6 Sodium lauryl sulfate 0.25 gulfonated dibenzothiophene dioxide 0 007g. Sulf n t d dib th r di d 4 -mercapto purine o a e enzo 10p ene 0x1 e N-vinyl- Z-pyrrolidone 0.2.1 Z-metcaptobenzimidazole 0.01 Sodium lauryl sulfate 0.5 N-v1ny1-2-pyrrohdone 1.0 Example 7 Sodium lauryl sulfate 0.5 Sulfonated dibenzothiophene dioxide 4 Example 19 @mFrcaPto purigm Q0075 gulfonatetd dibenzothiophene dioxide 6 s-i xa ia 0 5O dia 22335101.; 3 oiumaur suae y Example 8 Sodium lauryl sulfate 0,5 Sulfonated dibenzotbiophene dioxide I 1 Example 20 Sodium 1,3,6-naphthalene trisulfonate 10 sulfoflated dibenzothiopllefle dioxide 4 'N-viny1-2-pyrolidone 0,5 u -2- er apt benzumdazole 0.01 S dium lauryl sulfate 0.25 gtgfifig fi gg gi Example 9 Example 21 Slllfollated dillenzothiophene dioxide 4 0 s lf t d dibenzothiophene dioxide 4 P 2-butene-1,4-diol 0,2 z'buteneillpdlol Sodium lauryl qnlfate 025 Propargyl alcohol 0.005 2 butyne 1 4 dio1 0 01 Sodium lauryl sulfate 0.25 E '1'};

xamp e Example 10 Sulfonated dibenzothiophene dioxide 4 Sulfonated dibenzothiophene dioxide 4 'gg i' 1 3-me hy1-1-p ntyne-3-ol 0.012 F Z Z SEXEQ g; Sodlum lauryl Sulfate Sodium lauryl sulfate 025 Example Example SuLfonated dibenzothiophene dioxide 6 Sulfonated dibenzothiophene dioxide 4 Z-methyl-Pbutyne-Z-ol 0.012 2-(2-quino1y1methy1);isoquinolinium iodide 0.04 Sodium lauryl sulfate 0.25 Sodium lauryl su e I I 0.25

Example 24 I Amount, g./l. sulfonated dibenzothiophene dioxide 4 1 [2 (6 methylquinolyl)methylJpyridinium iodide 0.04 Sodium lauryl sulfate 0.25

Example 25 Sulfonated dibenzothiophene dioxide 4 l-(2-quinolylmethyl)pyridium iodide 0.04 Sodium lauryl sulfate 0.25

Example 26 Sulfonated dibenzothiophene dioxide 4 Sodium lauryl sulfate 0.25

-In Examples 27 and 28 the followingaqueous bath was used as a base solution:

The foregoing examples illustrate specific baths and processes, several being preferred. It is understood that the compositions and conditions may be varied. The sulfonated dibenzothiophene dioxide is also advantageously used in conjunction with another secondary brightener, as in Examples 2 and 8, to yield excellent bright deposits. The nickel from these baths may be applied to the usual basis metals including iron, steel, etc. They are preferably plated on copper or a copper alloy.

As many embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention includes all such modifications and variations as come within the scope of the appended claims.

We claim:

1. In an aqueous acid electrolytic bath containing soluble nickel salts for the electrodeposition of bright nickel, the improvement comprising incorporating therein as a brightener sulfonated dibenzothiophene dioxide having the structure wherein Y is selected from the group consisting of SO X and hydrogen, and X is a cation selected from the group consisting of hydrogen, ammonium, sodium, potassium, nickel, cobalt and magnesium, in an amount sufiicient to cause the electrodeposition of bright nickel from said bath.

2. In an aqueous acid electrolytic bath containing soluble nickel salts for the electrodeposition of bright nickel, the improvement comprising incorporating therein as a 6 I I brightener between 1 g./l. and 10 g./l. of sulfonated dibenzothiophene dioxides having the structure 0 0 wherein Y is selected from the group consisting of SO X and hydrogen, and X is a cation selected from the group consisting of hydrogen, ammonium, sodium, potassium, nickel, cobalt and magnesium, in an amount suflicient to cause the electrodeposition of bright nickel from said bath.

3. In an aqueous acid electrolytic bath containing soluble nickel salts for the electrodeposition of mirror-bright nickel and containing a primary brightener, the improvement comprising incorporating therein as a secondary brightener between 1 g./l. and 10 g./l. of at least one sulfonated dibenzothiophene dioxide having the structure wherein Y is selected from the group consisting of SO X and hydrogen, and X is a cation selected from the group consisting of hydrogen, ammonium, sodium, potassium, nickel, cobalt and magnesium.

4. In an aqueous acid electrolytic bath containing soluble nickel salts for the electrodeposition of mirror-bright nickel and containing a primary brightener, the improvement comprising incorporating therein as a secondary brightener between 2 g./l. and 6 g./l. of at least one sulfonated dibenzothiophene dioxide having the structure 7. The bath of claim No. 4 in which the primary brightener is used in amounts between .005 g./l.

8. In the process of electrodepositing bright nickel from an aqueous acid electrolytic bath containing soluble nickel salts, the improvement comprising incorporating therein as a brightener at least one sulfonated dibenzothiophene dioxide having the structure g./l. and .1

wherein Y is selected from the group consisting of SO X and hydrogen, and X is a cation selected from the class consisting of hydrogen, ammonium, sodium, potassium, nickel, cobalt and magnesium in an amount suflicient to cause the electrodeposition of bright nickel from said bath.

9. In the process of electrodepositing' mirror-bright nickel from an aqueous acid electrolytic bath containing soluble nickel salts and a primary brightener, the improve- 7 ment comprising incorporating therein as a secondary brightener between 1 g./l. and 10 g./l. of at least one sulfonateddibenzothiophene dioxide having the structure containing as a brightener a sulfonated dibenzothiophene dioxide anion having the structure wherein Y is selected from the group consisting of 80 and hydrogen, in an amount suflicient to cause the electrodeposition of bright nickel from said bath.

References Cited in the file of this patent UNITED STATES PATENTS 2,467,580 Brown Apr. 19, 1949 2,469,727 Hofiman May 10, 1949 2,849,353 Kardcs Aug. 26, 1958 

1. IN AN AQUEOUS ACID ELECTROLYTIC BATH CONTAINING SOLUBLE NICKEL SALTS FOR THE ELECTRODEPOSITION OF BRIGHT NICKEL, THE IMPROVEMENT COMPRISING INCORPORATING THEREIN AS A BRIGHTENER SULFONATED DIBENZOTHIOPHENE DIOXIDE HAVING THE STRUCTURE 